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Chapter 6

Chapter 6-Stress Disorders.doc

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Ayesha Khan

Abnormal PsychChapter 6 Stress DisordersHealth PsychologyExperiencing stress means experiencing events that we perceive as endangering our physical or psychological wellbeingThese events are usually referred to as stressors and peoples reactions to them are labeled stress responsesMost people as stressful perceive uncontrollable negative events such as the loss of a job the sudden death of a loved one or the loss of your home to a natural disasterAny negative event is perceived as more stressful if it is uncontrollableFor example in a classic experimental study participants were shown vivid photographs of victims of violent deaths One group of participants the experimental group could terminate their viewing by pressing a button The other group the control group could not terminate their viewing by pressing a button Both groups of participants saw the same photographs for the same duration of time The level of anxiety in both groups was measured by their galvanic skin response GSR a drop in the electrical resistance of the skin which is an index of physiological arousal The experimental group showed much less anxiety while viewing the photographs than did the control group even though the only difference between the groups was their control over their viewing Unpredictability also makes some events especially stressful Unpredictable events are more stressful than predictable eventsPredictable aversive events may also be less stressful because people know they can relax until they get the warning that the events are about to occur With unpredictable events people feel they can never relax because the events may occur at any time so they remain anxious all the time This explanation has been called the safety signal hypothesisAny change in life that requires numerous readjustmentseven a positive changecan be perceived as stressful A positive change can challenge our selfconcept or the limits of our capabilitiesNegative events are more likely than positive events to be perceived as stressful and to have impacts on physical and psychological healthNegative events often involve loss and can threaten a persons selfesteem or sense of mastery of the worldPhysiological Responses to StressWhen we face any type of stressora sabertoothed tiger a burglar with a weapon a first bungee jumpthe body mobilizes to handle the stressorThe liver releases extra sugar glucose to fuel our muscles and hormones are released to stimulate the conversion of fats and proteins to sugar The bodys metabolism increases in preparation for expending energy on physical action Heart rate blood pressure and breathing rate increase and the muscles tense Less essential activities such as digestion are curtailed Saliva and mucus dry up increasing the size of the air passages to the lungs The bodys natural painkillers endorphins are secreted and the surface blood vessels constrict to reduce bleeding in case of injury The spleen releases more red blood cells to help carry oxygenMost of these physiological changes result from the activation of two systems controlled by the hypothalamus heautonomic nervous system in particular the sympathetic division of this system and the adrenalcortical system a hormonereleasing system These physiological responses have developed through evolution to prepare the body to fight a threat or to flee from it and have been labeled the fightorflight response The hypothalamus first activates the sympathetic division of the autonomic nervous system The sympathetic system acts directly on the smooth muscles and internal organs to produce some of the bodily changesfor example increased heart rate and elevated blood pressure The sympathetic system also stimulates the release of a number of hormones including epinephrine adrenaline and norepinephrine which perpetuate a state of physiological arousalThe hypothalamus activates the adrenalcortical system by releasing corticotrophinrelease factor CRF which signals the pituitary gland to secrete adrenocorticotropic hormone ACTH the bodys major stress hormone ACTH stimulates the outer layer of the adrenal glands the adrenal cortex resulting in the release of a group of hormones the major one being cortisol The amount of cortisol in blood or urine samples is often used as a measure of stress ACTH also signals the adrenal glands to release about 30 other hormones each of which plays a role in the bodys adjustment to emergency situations Eventually the hormones signal the hippocampus a part of the brain that helps regulate emotions to turn off this physiological cascade when the threatening stimulus has passed The fightorflight system thus has its own feedback loop which normally regulates the level of physiological arousal experienced in response to a stressor This response is very adaptive when the stressor or threat is immediate and fight or flight is possible and useful However when a stressor is chronic and a person or an animal cannot fight it or flee from it the chronic physiological arousal that results can be severely damaging to the body Described such physiological changes as part of the general adaptation syndrome that all organisms show in response to stress The general adaptation syndrome consists of three phasesFirst phase alarm the body mobilizes to confront a threat by triggeringsympathetic nervous system activityThe second phase resistance the organism makes efforts to cope with the threat by fighting it or fleeing from it
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